1. Field of the Invention
The present invention relates generally to design of electronic circuits, and more specifically to a scannable memory cell used in integrated circuit design.
2. Related Art
A scan based test generally refers to an approach in which storage elements of an integrated circuit are connected as a scan chain, a scan vector is scanned in through the scan chain, the integrated circuit is placed in an evaluation mode for one or more clock cycles, and the values stored due to evaluation are compared with an expected output to determine whether the integrated circuit is operating as desired or not.
On the other hand, functional mode refers to the normal operation mode of an integrated circuit, providing the general utility the circuit is designed for.
To support both the scan based tests and the functional mode of operations, additional circuitry is often provided associated with each storage element (sought to be part of a scan chain and the functional mode of operation). The additional circuitry enables the bits of the scan vector to be received and stored in the storage element during the scan operations, and the bits from a portion of the integrated circuit during functional mode operations according to (or determined by) the topology/connectivity with which the integrated circuit is designed.
The storage element along with the additional circuitry provided associated with the storage element, may together be referred to as a memory cell.
There are several situations in which it is desirable that the memory cells operate with low delay in functional mode. For example, if a memory cell is in the critical path of a circuit, it may be desirable to reduce in the delay of the memory cell in the functional mode. Various aspects of the present invention provide for such a memory cell as described below in further detail.
In the drawings, like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements. The drawing in which an element first appears is indicated by the leftmost digit(s) in the corresponding reference number.